Efforts are being made in aircraft construction to employ components on an increasing scale that consist completely or partly of fibre-reinforced composite materials, for example carbon-fibre-reinforced plastics (CFRP), as load-bearing components. For example, DE 10 2007 062 111 A1 describes a transverse-member structure consisting of carbon-fibre-reinforced plastic, which serves for supporting the individual panels of an aircraft-floor system for separating a passenger cabin from a cargo compartment arranged below the passenger cabin. Furthermore, it is likewise known from DE 10 2007 062 111 A1, for example, to employ components realised in a sandwich construction, with a core and also with top layers, applied onto the core, consisting of a fibre-reinforced plastic material, as floor panels or ceiling panels in an aircraft.
For the purpose of producing components from fibre-reinforced composite materials, as a rule the reinforcing fibres are firstly introduced into a moulding tool. Subsequently the fibres are impregnated with the matrix material which is usually present in liquid form. Finally, curing of the matrix material is effected by appropriate control of temperature and/or pressure. Known methods for producing components from fibre-reinforced composite materials include injection methods, wherein the liquid matrix material is injected into a closed moulding tool under elevated pressure of over 6 bar. Furthermore, infusion methods are known, wherein the reinforcing fibres are inserted into an open moulding tool and are covered with a semipermeable membrane that is pervious to gases but impervious to the matrix material. The semipermeable membrane is covered by a gas-impervious film, so that an underpressure can be applied between the semipermeable membrane and the gas-impervious film and, as a result, liquid matrix material can be sucked into the moulding tool.
Irrespective of whether an injection method or an infusion method is employed for producing a component from a fibre-reinforced composite material, the control of the flow of matrix material into and through the moulding tool is of crucial importance for the quality of the component. Therefore in the case of production of the component by an infusion method with an open moulding tool the flow of matrix material is ordinarily monitored by means of a CCD camera. In the case of production of the component by an injection method with a closed moulding tool, on the other hand, visual monitoring of the flow of matrix material is not possible, so that sensors such as, for example, ultrasonic sensors, line sensors operating capacitively, temperature sensors or pressure sensors come into operation here. As a rule, however, sensor-based measuring principles of such a type are not capable of being employed in real time, by reason of the fact that the sensors can only detect changes in the corresponding physical measured quantities associated with the actual advance of the front of matrix material.